Downlink control information response to idle mode requests

ABSTRACT

Methods, systems, and devices for wireless communications are described. A user equipment (UE) may transmit a request message to a base station while operating in an idle mode. The base station may generate, in response to the request message, a response message including a random access preamble index corresponding to the received request message. In some cases, the base station may determine a radio network temporary identifier (RNTI) based on the random access preamble index and scramble a cyclic redundancy check (CRC) of the response message with the RNTI. In some examples, the random access preamble index may be included in a payload of the response message. The UE may monitor a physical downlink control channel for the response message to the request message and receive the response message on the physical downlink control channel.

CROSS REFERENCE

The present Application for Patent is a Continuation of U.S. patentapplication Ser. No. 16/516,164 by AKKARAKARAN et al., entitled“DOWNLINK CONTROL INFORMATION RESPONSE TO IDLE MODE REQUESTS” filed Jul.18, 2019, which claims the benefit of U.S. Provisional PatentApplication No. 62/701,426 by AKKARAKARN et al., entitled “DOWNLINKCONTROL INFORMATION RESPONSE TO IDLE MODE REQUESTS,” filed Jul. 20,2018, assigned to the assignee hereof, and expressly incorporated hereinby reference.

FIELD OF TECHNOLOGY

The following relates generally to wireless communications, and morespecifically to downlink control information response to idle moderequests.

BACKGROUND

Wireless communications systems are widely deployed to provide varioustypes of communication content such as voice, video, packet data,messaging, broadcast, and so on. These systems may be capable ofsupporting communication with multiple users by sharing the availablesystem resources (e.g., time, frequency, and power). Examples of suchmultiple-access systems include fourth generation (4G) systems such asLong Term Evolution (LTE) systems, LTE-Advanced (LTE-A) systems, orLTE-A Pro systems, and fifth generation (5G) systems which may bereferred to as New Radio (NR) systems. These systems may employtechnologies such as code division multiple access (CDMA), time divisionmultiple access (TDMA), frequency division multiple access (FDMA),orthogonal frequency division multiple access (OFDMA), or discreteFourier transform-spread-OFDM (DFT-S-OFDM). A wireless multiple-accesscommunications system may include a number of base stations or networkaccess nodes, each simultaneously supporting communication for multiplecommunication devices, which may be otherwise known as user equipment(UE).

A UE may lose system information while operating in an idle mode. Thesystem information may be used to communicate with a serving basestation. Conventional techniques for providing system information to theUE are deficient.

SUMMARY

A user equipment (UE) operating in an idle mode may transmit a requestfor system information to the base station. The request message mayinclude a preamble, such as a physical random access channel (PRACH)preamble, associated with the system information being requested. Thebase station may receive the request message and generate a responsemessage (e.g., a random access response). The response message mayinclude a random access preamble identifier (RAPID) or random accesspreamble index, which indicates the preamble used by the UE to requestsystem information. The UE may receive the response message, determinethe RAPID corresponds to the preamble included in the request message,and determine it is the correct recipient for the response message.Then, from the response message, the UE may identify timing or frequencyinformation for when the requested system information will betransmitted by the base station.

In some other wireless communications system, a base station maytransmit a physical downlink control channel (PDCCH) signal to scheduleresources for a physical downlink shared channel (PDSCH) signal andtransmit the preamble index in the PDSCH signal. However, allocatingresources for a PDSCH signal just to transmit the preamble index may bean inefficient use of resources, as the preamble index may only be a fewbits. Instead, the base station may include a random access responsepayload in the PDCCH signal. Thus, the base station may transmit theresponse message using just the PDCCH signal, and the base station maynot schedule a PDSCH message as part of the response message. Forexample, the base station may transmit the response message using just aPDCCH message, and not a PDSCH message if the base station has just onerandom access response to transmit. Techniques for transmitting aresponse to an idle-mode request using a PDCCH and without using a PDSCHare described herein.

A method of wireless communications is described. The method may includetransmitting a request message to a base station while operating in anidle mode, monitoring a physical downlink control channel for a responsemessage including a random access preamble index associated with therequest message, and receiving the response message on the physicaldownlink control channel.

An apparatus for wireless communications is described. The apparatus mayinclude a processor, memory in electronic communication with theprocessor, and instructions stored in the memory. The instructions maybe executable by the processor to cause the apparatus to transmit arequest message to a base station while operating in an idle mode,monitor a physical downlink control channel for a response messageincluding a random access preamble index associated with the requestmessage, and receive the response message on the physical downlinkcontrol channel.

Another apparatus for wireless communications is described. Theapparatus may include means for transmitting a request message to a basestation while operating in an idle mode, monitoring a physical downlinkcontrol channel for a response message including a random accesspreamble index associated with the request message, and receiving theresponse message on the physical downlink control channel.

A non-transitory computer-readable medium storing code for wirelesscommunications is described. The code may include instructionsexecutable by a processor to transmit a request message to a basestation while operating in an idle mode, monitor a physical downlinkcontrol channel for a response message including a random accesspreamble index associated with the request message, and receive theresponse message on the physical downlink control channel.

Some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein may further includeoperations, features, means, or instructions for determining a radionetwork temporary identifier (RNTI) based on the random access preambleindex and unscrambling a CRC of the response message with the RNTI.

Some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein may further includeoperations, features, means, or instructions for identifying a bit fieldpattern indicating a RNTI for the response message may be calculatedbased on the random access preamble index.

Some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein may further includeoperations, features, means, or instructions for identifying a firstsubset of bits of the random access preamble index in a RNTI andidentifying a second subset of bits of the random access preamble indexin a payload of the response message.

Some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein may further includeoperations, features, means, or instructions for identifying the randomaccess preamble index in a payload of the response message.

Some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein may further includeoperations, features, means, or instructions for identifying a payloadof the response message based on a value of a frequency assignment bitfield of the response message.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, the payload may be furtheridentified based on one or more reserved bits of the response message.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, the received response messagemay be an acknowledgment of the request message.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, the received response messageincludes information in response to the request message.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, the request message may be asystem information request and the information in response to therequest message includes timing or frequency information related to whena requested system information will be transmitted.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, the request message may be apositioning reference signal (PRS) request, and the information inresponse to the request message includes a configuration for a PRS to betransmitted in response to the request.

Some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein may further includeoperations, features, means, or instructions for monitoring for thereceived response message on the physical downlink control channel basedon the response message including a single random access response.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, a type of the generatedresponse message may be indicated by a type-identifying field in a RNTI.

A method of wireless communications is described. The method may includereceiving a request message from a UE operating in an idle mode,generating a response message including a random access preamble indexcorresponding to the received request message, and transmitting thegenerated response message on a physical downlink control channel.

An apparatus for wireless communications is described. The apparatus mayinclude a processor, memory in electronic communication with theprocessor, and instructions stored in the memory. The instructions maybe executable by the processor to cause the apparatus to receive arequest message from a UE operating in an idle mode, generate a responsemessage including a random access preamble index corresponding to thereceived request message, and transmit the generated response message ona physical downlink control channel.

Another apparatus for wireless communications is described. Theapparatus may include means for receiving a request message from a UEoperating in an idle mode, generating a response message including arandom access preamble index corresponding to the received requestmessage, and transmitting the generated response message on a physicaldownlink control channel.

A non-transitory computer-readable medium storing code for wirelesscommunications is described. The code may include instructionsexecutable by a processor to receive a request message from a UEoperating in an idle mode, generate a response message including arandom access preamble index corresponding to the received requestmessage, and transmit the generated response message on a physicaldownlink control channel.

Some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein may further includeoperations, features, means, or instructions for determining a RNTIbased on the random access preamble index and scrambling a CRC of thegenerated response message with the determined RNTI.

Some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein may further includeoperations, features, means, or instructions for setting a bit fieldpattern of the generated response message indicating a RNTI may becalculated based on the random access preamble index.

Some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein may further includeoperations, features, means, or instructions for including a firstsubset of bits of the random access preamble index in a RNTI andincluding a second subset of bits of the random access preamble index ina payload of the generated response message.

Some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein may further includeoperations, features, means, or instructions for determining a payloadfor the generated response message including the random access preambleindex.

Some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein may further includeoperations, features, means, or instructions for indicating a payloadfor the generated response message includes the random access preambleindex based on a value of a frequency assignment bit field.

Some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein may further includeoperations, features, means, or instructions for indicating the payloadincludes the random access preamble index may be further based on one ormore reserved bits of the generated response message.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, the generated responsemessage may be an acknowledgment of the request message.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, the generated responsemessage includes information in response to the request message.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, the request message may be asystem information request and the information in response to therequest message includes timing or frequency information related to whena requested system information will be transmitted.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, the request message may be aPRS request, and the information in response to the request messageincludes a configuration for a PRS to be transmitted in response to therequest.

Some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein may further includeoperations, features, means, or instructions for identifying a singlerandom access response for the response message, where the generatedresponse message may be transmitted on the physical downlink controlchannel based on the identifying.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, a type of the generatedresponse message may be indicated by a type-identifying field in a RNTI.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example of a system for wireless communications inaccordance with aspects of the present disclosure.

FIG. 2 illustrates an example of a wireless communications system inaccordance with aspects of the present disclosure.

FIG. 3 illustrates an example of a process flow in accordance withaspects of the present disclosure.

FIGS. 4 and 5 show block diagrams of devices in accordance with aspectsof the present disclosure.

FIG. 6 shows a block diagram of a communications manager in accordancewith aspects of the present disclosure.

FIG. 7 shows a diagram of a system including a device in accordance withaspects of the present disclosure.

FIGS. 8 and 9 show block diagrams of devices in accordance with aspectsof the present disclosure.

FIG. 10 shows a block diagram of a communications manager in accordancewith aspects of the present disclosure.

FIG. 11 shows a diagram of a system including a device in accordancewith aspects of the present disclosure.

FIGS. 12 through 17 show flowcharts illustrating methods in accordancewith aspects of the present disclosure.

DETAILED DESCRIPTION

A user equipment (UE) may operate in an idle mode to conserve powerusage. However, while operating in idle mode, the UE may lose someconfigurations for wireless communications, or the configurations maychange while the UE is in idle mode. For example, the UE may lose thesystem information, or the system information may have been updatedwhile the UE was in idle mode. The UE may wake up and monitor for asynchronization signal block (SSB) which is periodically transmitted bya base station. The UE may receive a physical random access channel(PRACH) configuration and a configuration for transmitting a request forsystem information. This may allow the network to reduce or turn off theperiodic broadcast of system information and instead send it only uponrequest, improving system resource utilization.

The UE may transmit a request message for system information to the basestation. The request message may include a preamble, such as a PRACHpreamble, associated with the system information being requested. The UEmay identify PRACH sequences to use in the request message based on thePRACH configuration. The base station may receive the request messageand generate a response message (e.g., a random access response). Theresponse message may include a random access preamble index (RAPID)which indicates the preamble used by the UE to request systeminformation. The RAPID may correspond to the preamble index used totransmit the request message, where the response message is transmittedin response to the request message. The UE may receive the responsemessage, determine the RAPID corresponds to the preamble included in therequest message, and determine it is the correct recipient for theresponse message. Then, from the response message, the UE may identifytiming or frequency information for when the requested systeminformation will be transmitted by the base station.

In some other wireless communications system, a base station maytransmit a PDCCH signal which schedules resources for a PDSCH signal.The base station transmits the preamble index in the PDSCH signal.However, allocating resources for a PDSCH signal just to transmit thepreamble index may be an inefficient use of resources, as the preambleindex may only be a few bits.

Instead, the base station may include a random access response payloadin the PDCCH signal or PDCCH message. Thus, the base station maytransmit the response message using just the PDCCH message, and the basestation may not schedule a PDSCH signal as part of the response message.For example, the base station may transmit the response message usingjust a PDCCH message, and not a PDSCH message, if the base station hasjust one random access response to transmit. In some examples, such asif there are multiple random access responses to be transmitted, thePDCCH may not have sufficient capacity to accommodate all of them, andthe response may be transmitted using a PDCCH that schedules the PDSCHcarrying all the responses.

In a first example, the base station may use the RAPID to determine amodified radio network temporary identifier (RNTI). The modified RNTImay be determined based on the resource allocation and preamble of therequest message. The base station may scramble a cyclic redundancy check(CRC) of the response message with the modified RNTI. In some cases, thebase station may use a bitfield pattern to distinguish the modified RNTIfrom other (e.g., non-modified) RNTIs. In some cases, the RAPID may notbe included in the PDCCH payload. In other examples, a portion of theRAPID may be used to generate the modified RNTI, and a remaining portionof the RAPID may be included in the PDCCH payload. The modified RNTI maybe an example of a modified random access RNTI (RA-RNTI).

In a second example, the RAPID may be included in the PDCCH payload. Insome cases, the base station may indicate the presence of the RAPID inthe PDCCH payload based on a value of a frequency assignment field. ThePDCCH message (e.g., the response message) may have a DCI formatnormally used to schedule a PDSCH. Therefore, if a frequency assignmentfield is set to a special value, this may be an indication to the UEthat the PDCCH message may be used for conveying the RAPID instead ofscheduling PDSCH. Additionally, or alternatively, the base station mayindicate the RAPID is in the PDCCH payload based on one or more reservedbits

More generally, there may be a combination of bitfields with aparticular value of bit assignments that are not used or not allowed forexisting DCI formats addressed to the same RNTI. There may then be a newDCI format addressed to that RNTI as having those bitfields set to theidentified bit assignments, with remaining bits usable to carryadditional information required. Thus, the base station 105 may indicatethe new DCI format based on a particular value of bit assignments. Forexample, the additional information may be the RAPID to be acknowledgedby the PDCCH, and possibly other information related to the idle moderequest corresponding to the transmitted PRACH preamble with that RAPID.When the idle mode request is a System Information (SI) request, theadditional information may indicate the time and/or frequency locationat which the SI will be transmitted, which may reduce the UE'scomplexity in monitoring for this SI. The frequency assignment bitfieldset to all ones is a particular case of such a bitfield and assignment.For example, the frequency assignment bitfield set to all ones may beused for PDCCH addressed to RA-RNTI. In some cases, the frequencyassignment set to all ones may be used in other configurations toindicate downlink DCI for PDCCH-ordered RACH when PDCCH is addressed toa cell-RNTI

The techniques described herein may be used for other idle moderequests. For example, the UE and base station may implement similartechniques to handle an idle mode request for a downlink or uplinkpositioning reference signal (PRS). The PDCCH payload may also includeother parameters related to the PRS configuration. By using a modifiedRNTI, the base station may define a new payload format and use remainingavailable bits in the PDCCH payload for the configuration information.In some cases, each idle mode request type may be associated with a typeID field in a modified RNTI used to scramble the CRC of the PDCCHtransmitted in response to the idle mode request. In other cases,multiple idle mode request responses may be addressed to the same RNTI(for example, the RA-RNTI), and specific bitfields in the PDCCH payloadmay be used to establish the type of idle mode request beingacknowledged. For example, the type of idle mode request may beidentified by the RAPID included in the PDCCH payload as describedabove, and other unused bits in the PDCCH payload may then represent orindicate specific configuration information related to the specific idlemode request.

Aspects of the disclosure are initially described in the context of awireless communications system. Aspects of the disclosure are furtherillustrated by and described with reference to apparatus diagrams,system diagrams, and flowcharts that relate to downlink controlinformation response to idle mode requests.

FIG. 1 illustrates an example of a wireless communications system 100 inaccordance with aspects of the present disclosure. The wirelesscommunications system 100 includes base stations 105, UEs 115, and acore network 130. In some examples, the wireless communications system100 may be a Long Term Evolution (LTE) network, an LTE-Advanced (LTE-A)network, an LTE-A Pro network, or a New Radio (NR) network. In somecases, wireless communications system 100 may support enhanced broadbandcommunications, ultra-reliable (e.g., mission critical) communications,low latency communications, or communications with low-cost andlow-complexity devices.

Base stations 105 may wirelessly communicate with UEs 115 via one ormore base station antennas. Base stations 105 described herein mayinclude or may be referred to by those skilled in the art as a basetransceiver station, a radio base station, an access point, a radiotransceiver, a NodeB, an eNodeB (eNB), a next-generation Node B orgiga-nodeB (either of which may be referred to as a gNB), a Home NodeB,a Home eNodeB, or some other suitable terminology. Wirelesscommunications system 100 may include base stations 105 of differenttypes (e.g., macro or small cell base stations). The UEs 115 describedherein may be able to communicate with various types of base stations105 and network equipment including macro eNBs, small cell eNBs, gNBs,relay base stations, and the like.

Each base station 105 may be associated with a particular geographiccoverage area 110 in which communications with various UEs 115 issupported. Each base station 105 may provide communication coverage fora respective geographic coverage area 110 via communication links 125,and communication links 125 between a base station 105 and a UE 115 mayutilize one or more carriers. Communication links 125 shown in wirelesscommunications system 100 may include uplink transmissions from a UE 115to a base station 105, or downlink transmissions from a base station 105to a UE 115. Downlink transmissions may also be called forward linktransmissions while uplink transmissions may also be called reverse linktransmissions.

The geographic coverage area 110 for a base station 105 may be dividedinto sectors making up only a portion of the geographic coverage area110, and each sector may be associated with a cell. For example, eachbase station 105 may provide communication coverage for a macro cell, asmall cell, a hot spot, or other types of cells, or various combinationsthereof. In some examples, a base station 105 may be movable andtherefore provide communication coverage for a moving geographiccoverage area 110. In some examples, different geographic coverage areas110 associated with different technologies may overlap, and overlappinggeographic coverage areas 110 associated with different technologies maybe supported by the same base station 105 or by different base stations105. The wireless communications system 100 may include, for example, aheterogeneous LTE/LTE-A/LTE-A Pro or NR network in which different typesof base stations 105 provide coverage for various geographic coverageareas 110.

The term “cell” refers to a logical communication entity used forcommunication with a base station 105 (e.g., over a carrier), and may beassociated with an identifier for distinguishing neighboring cells(e.g., a physical cell identifier (PCID), a virtual cell identifier(VCID)) operating via the same or a different carrier. In some examples,a carrier may support multiple cells, and different cells may beconfigured according to different protocol types (e.g., machine-typecommunication (MTC), narrowband Internet-of-Things (NB-IoT), enhancedmobile broadband (eMBB), or others) that may provide access fordifferent types of devices. In some cases, the term “cell” may refer toa portion of a geographic coverage area 110 (e.g., a sector) over whichthe logical entity operates.

UEs 115 may be dispersed throughout the wireless communications system100, and each UE 115 may be stationary or mobile. A UE 115 may also bereferred to as a mobile device, a wireless device, a remote device, ahandheld device, or a subscriber device, or some other suitableterminology, where the “device” may also be referred to as a unit, astation, a terminal, or a client. A UE 115 may also be a personalelectronic device such as a cellular phone, a personal digital assistant(PDA), a tablet computer, a laptop computer, or a personal computer. Insome examples, a UE 115 may also refer to a wireless local loop (WLL)station, an Internet of Things (IoT) device, an Internet of Everything(IoE) device, or an MTC device, or the like, which may be implemented invarious articles such as appliances, vehicles, meters, or the like.

Some UEs 115, such as MTC or IoT devices, may be low cost or lowcomplexity devices, and may provide for automated communication betweenmachines (e.g., via Machine-to-Machine (M2M) communication). M2Mcommunication or MTC may refer to data communication technologies thatallow devices to communicate with one another or a base station 105without human intervention. In some examples, M2M communication or MTCmay include communications from devices that integrate sensors or metersto measure or capture information and relay that information to acentral server or application program that can make use of theinformation or present the information to humans interacting with theprogram or application. Some UEs 115 may be designed to collectinformation or enable automated behavior of machines. Examples ofapplications for MTC devices include smart metering, inventorymonitoring, water level monitoring, equipment monitoring, healthcaremonitoring, wildlife monitoring, weather and geological eventmonitoring, fleet management and tracking, remote security sensing,physical access control, and transaction-based business charging.

Some UEs 115 may be configured to employ operating modes that reducepower consumption, such as half-duplex communications (e.g., a mode thatsupports one-way communication via transmission or reception, but nottransmission and reception simultaneously). In some examples half-duplexcommunications may be performed at a reduced peak rate. Other powerconservation techniques for UEs 115 include entering a power saving“deep sleep” mode when not engaging in active communications, oroperating over a limited bandwidth (e.g., according to narrowbandcommunications). In some cases, UEs 115 may be designed to supportcritical functions (e.g., mission critical functions), and a wirelesscommunications system 100 may be configured to provide ultra-reliablecommunications for these functions.

In some cases, a UE 115 may also be able to communicate directly withother UEs 115 (e.g., using a peer-to-peer (P2P) or device-to-device(D2D) protocol). One or more of a group of UEs 115 utilizing D2Dcommunications may be within the geographic coverage area 110 of a basestation 105. Other UEs 115 in such a group may be outside the geographiccoverage area 110 of a base station 105, or be otherwise unable toreceive transmissions from a base station 105. In some cases, groups ofUEs 115 communicating via D2D communications may utilize a one-to-many(1:M) system in which each UE 115 transmits to every other UE 115 in thegroup. In some cases, a base station 105 facilitates the scheduling ofresources for D2D communications. In other cases, D2D communications arecarried out between UEs 115 without the involvement of a base station105.

Base stations 105 may communicate with the core network 130 and with oneanother. For example, base stations 105 may interface with the corenetwork 130 through backhaul links 132 (e.g., via an S1, N2, N3, orother interface). Base stations 105 may communicate with one anotherover backhaul links 134 (e.g., via an X2, Xn, or other interface) eitherdirectly (e.g., directly between base stations 105) or indirectly (e.g.,via core network 130).

The core network 130 may provide user authentication, accessauthorization, tracking, Internet Protocol (IP) connectivity, and otheraccess, routing, or mobility functions. The core network 130 may be anevolved packet core (EPC), which may include at least one mobilitymanagement entity (MME), at least one serving gateway (S-GW), and atleast one Packet Data Network (PDN) gateway (P-GW). The MME may managenon-access stratum (e.g., control plane) functions such as mobility,authentication, and bearer management for UEs 115 served by basestations 105 associated with the EPC. User IP packets may be transferredthrough the S-GW, which itself may be connected to the P-GW. The P-GWmay provide IP address allocation as well as other functions. The P-GWmay be connected to the network operators IP services. The operators IPservices may include access to the Internet, Intranet(s), an IPMultimedia Subsystem (IMS), or a Packet-Switched (PS) Streaming Service.

At least some of the network devices, such as a base station 105, mayinclude subcomponents such as an access network entity, which may be anexample of an access node controller (ANC). Each access network entitymay communicate with UEs 115 through a number of other access networktransmission entities, which may be referred to as a radio head, a smartradio head, or a transmission/reception point (TRP). In someconfigurations, various functions of each access network entity or basestation 105 may be distributed across various network devices (e.g.,radio heads and access network controllers) or consolidated into asingle network device (e.g., a base station 105).

Wireless communications system 100 may operate using one or morefrequency bands, typically in the range of 300 MHz to 300 GHz.Generally, the region from 300 MHz to 3 GHz is known as the ultra-highfrequency (UHF) region or decimeter band, since the wavelengths rangefrom approximately one decimeter to one meter in length. UHF waves maybe blocked or redirected by buildings and environmental features.However, the waves may penetrate structures sufficiently for a macrocell to provide service to UEs 115 located indoors. Transmission of UHFwaves may be associated with smaller antennas and shorter range (e.g.,less than 100 km) compared to transmission using the smaller frequenciesand longer waves of the high frequency (HF) or very high frequency (VHF)portion of the spectrum below 300 MHz.

Wireless communications system 100 may also operate in a super highfrequency (SHF) region using frequency bands from 3 GHz to 30 GHz, alsoknown as the centimeter band. The SHF region includes bands such as the5 GHz industrial, scientific, and medical (ISM) bands, which may be usedopportunistically by devices that can tolerate interference from otherusers.

Wireless communications system 100 may also operate in an extremely highfrequency (EHF) region of the spectrum (e.g., from 30 GHz to 300 GHz),also known as the millimeter band. In some examples, wirelesscommunications system 100 may support millimeter wave (mmW)communications between UEs 115 and base stations 105, and EHF antennasof the respective devices may be even smaller and more closely spacedthan UHF antennas. In some cases, this may facilitate use of antennaarrays within a UE 115. However, the propagation of EHF transmissionsmay be subject to even greater atmospheric attenuation and shorter rangethan SHF or UHF transmissions. Techniques disclosed herein may beemployed across transmissions that use one or more different frequencyregions, and designated use of bands across these frequency regions maydiffer by country or regulating body.

In some cases, wireless communications system 100 may utilize bothlicensed and unlicensed radio frequency spectrum bands. For example,wireless communications system 100 may employ License Assisted Access(LAA), LTE-Unlicensed (LTE-U) radio access technology, or NR technologyin an unlicensed band such as the 5 GHz ISM band. When operating inunlicensed radio frequency spectrum bands, wireless devices such as basestations 105 and UEs 115 may employ listen-before-talk (LBT) proceduresto ensure a frequency channel is clear before transmitting data. In somecases, operations in unlicensed bands may be based on a CA configurationin conjunction with CCs operating in a licensed band (e.g., LAA).Operations in unlicensed spectrum may include downlink transmissions,uplink transmissions, peer-to-peer transmissions, or a combination ofthese. Duplexing in unlicensed spectrum may be based on frequencydivision duplexing (FDD), time division duplexing (TDD), or acombination of both.

In some examples, base station 105 or UE 115 may be equipped withmultiple antennas, which may be used to employ techniques such astransmit diversity, receive diversity, multiple-input multiple-output(MIMO) communications, or beamforming. For example, wirelesscommunications system 100 may use a transmission scheme between atransmitting device (e.g., a base station 105) and a receiving device(e.g., a UE 115), where the transmitting device is equipped withmultiple antennas and the receiving devices are equipped with one ormore antennas. MIMO communications may employ multipath signalpropagation to increase the spectral efficiency by transmitting orreceiving multiple signals via different spatial layers, which may bereferred to as spatial multiplexing. The multiple signals may, forexample, be transmitted by the transmitting device via differentantennas or different combinations of antennas. Likewise, the multiplesignals may be received by the receiving device via different antennasor different combinations of antennas. Each of the multiple signals maybe referred to as a separate spatial stream, and may carry bitsassociated with the same data stream (e.g., the same codeword) ordifferent data streams. Different spatial layers may be associated withdifferent antenna ports used for channel measurement and reporting. MIMOtechniques include single-user MIMO (SU-MIMO) where multiple spatiallayers are transmitted to the same receiving device, and multiple-userMIMO (MU-MIMO) where multiple spatial layers are transmitted to multipledevices.

Beamforming, which may also be referred to as spatial filtering,directional transmission, or directional reception, is a signalprocessing technique that may be used at a transmitting device or areceiving device (e.g., a base station 105 or a UE 115) to shape orsteer an antenna beam (e.g., a transmit beam or receive beam) along aspatial path between the transmitting device and the receiving device.Beamforming may be achieved by combining the signals communicated viaantenna elements of an antenna array such that signals propagating atparticular orientations with respect to an antenna array experienceconstructive interference while others experience destructiveinterference. The adjustment of signals communicated via the antennaelements may include a transmitting device or a receiving deviceapplying certain amplitude and phase offsets to signals carried via eachof the antenna elements associated with the device. The adjustmentsassociated with each of the antenna elements may be defined by abeamforming weight set associated with a particular orientation (e.g.,with respect to the antenna array of the transmitting device orreceiving device, or with respect to some other orientation).

In one example, a base station 105 may use multiple antennas or antennaarrays to conduct beamforming operations for directional communicationswith a UE 115. For instance, some signals (e.g., synchronizationsignals, reference signals, beam selection signals, or other controlsignals) may be transmitted by a base station 105 multiple times indifferent directions, which may include a signal being transmittedaccording to different beamforming weight sets associated with differentdirections of transmission. Transmissions in different beam directionsmay be used to identify (e.g., by the base station 105 or a receivingdevice, such as a UE 115) a beam direction for subsequent transmissionand/or reception by the base station 105. Some signals, such as datasignals associated with a particular receiving device, may betransmitted by a base station 105 in a single beam direction (e.g., adirection associated with the receiving device, such as a UE 115). Insome examples, the beam direction associated with transmissions along asingle beam direction may be determined based at least in in part on asignal that was transmitted in different beam directions. For example, aUE 115 may receive one or more of the signals transmitted by the basestation 105 in different directions, and the UE 115 may report to thebase station 105 an indication of the signal it received with a highestsignal quality, or an otherwise acceptable signal quality. Althoughthese techniques are described with reference to signals transmitted inone or more directions by a base station 105, a UE 115 may employsimilar techniques for transmitting signals multiple times in differentdirections (e.g., for identifying a beam direction for subsequenttransmission or reception by the UE 115), or transmitting a signal in asingle direction (e.g., for transmitting data to a receiving device).

A receiving device (e.g., a UE 115, which may be an example of a mmWreceiving device) may try multiple receive beams when receiving varioussignals from the base station 105, such as synchronization signals,reference signals, beam selection signals, or other control signals. Forexample, a receiving device may try multiple receive directions byreceiving via different antenna subarrays, by processing receivedsignals according to different antenna subarrays, by receiving accordingto different receive beamforming weight sets applied to signals receivedat a plurality of antenna elements of an antenna array, or by processingreceived signals according to different receive beamforming weight setsapplied to signals received at a plurality of antenna elements of anantenna array, any of which may be referred to as “listening” accordingto different receive beams or receive directions. In some examples areceiving device may use a single receive beam to receive along a singlebeam direction (e.g., when receiving a data signal). The single receivebeam may be aligned in a beam direction determined based at least inpart on listening according to different receive beam directions (e.g.,a beam direction determined to have a highest signal strength, highestsignal-to-noise ratio, or otherwise acceptable signal quality based atleast in part on listening according to multiple beam directions).

In some cases, the antennas of a base station 105 or UE 115 may belocated within one or more antenna arrays, which may support MIMOoperations, or transmit or receive beamforming. For example, one or morebase station antennas or antenna arrays may be co-located at an antennaassembly, such as an antenna tower. In some cases, antennas or antennaarrays associated with a base station 105 may be located in diversegeographic locations. A base station 105 may have an antenna array witha number of rows and columns of antenna ports that the base station 105may use to support beamforming of communications with a UE 115.Likewise, a UE 115 may have one or more antenna arrays that may supportvarious MIMO or beamforming operations.

In some cases, wireless communications system 100 may be a packet-basednetwork that operate according to a layered protocol stack. In the userplane, communications at the bearer or Packet Data Convergence Protocol(PDCP) layer may be IP-based. A Radio Link Control (RLC) layer may insome cases perform packet segmentation and reassembly to communicateover logical channels. A Medium Access Control (MAC) layer may performpriority handling and multiplexing of logical channels into transportchannels. The MAC layer may also use hybrid automatic repeat request(HARQ) to provide retransmission at the MAC layer to improve linkefficiency. In the control plane, the Radio Resource Control (RRC)protocol layer may provide establishment, configuration, and maintenanceof an RRC connection between a UE 115 and a base station 105 or corenetwork 130 supporting radio bearers for user plane data. At thePhysical (PHY) layer, transport channels may be mapped to physicalchannels.

In some cases, UEs 115 and base stations 105 may support retransmissionsof data to increase the likelihood that data is received successfully.HARQ feedback is one technique of increasing the likelihood that data isreceived correctly over a communication link 125. HARQ may include acombination of error detection (e.g., using a CRC), forward errorcorrection (FEC), and retransmission (e.g., automatic repeat request(ARQ)). HARQ may improve throughput at the MAC layer in poor radioconditions (e.g., signal-to-noise conditions). In some cases, a wirelessdevice may support same-slot HARQ feedback, where the device may provideHARQ feedback in a specific slot for data received in a previous symbolin the slot. In other cases, the device may provide HARQ feedback in asubsequent slot, or according to some other time interval.

Time intervals in LTE or NR may be expressed in multiples of a basictime unit, which may, for example, refer to a sampling period of T_(s)=1/30,720,000 seconds. Time intervals of a communications resource may beorganized according to radio frames each having a duration of 10milliseconds (ms), where the frame period may be expressed asT_(f)=307,200 T_(s). The radio frames may be identified by a systemframe number (SFN) ranging from 0 to 1023. Each frame may include 10subframes numbered from 0 to 9, and each subframe may have a duration of1 ms. A subframe may be further divided into 2 slots each having aduration of 0.5 ms, and each slot may contain 6 or 7 modulation symbolperiods (e.g., depending on the length of the cyclic prefix prepended toeach symbol period). Excluding the cyclic prefix, each symbol period maycontain 2048 sampling periods. In some cases, a subframe may be thesmallest scheduling unit of the wireless communications system 100, andmay be referred to as a transmission time interval (TTI). In othercases, a smallest scheduling unit of the wireless communications system100 may be shorter than a subframe or may be dynamically selected (e.g.,in bursts of shortened TTIs (sTTIs) or in selected component carriersusing sTTIs).

In some wireless communications systems, a slot may further be dividedinto multiple mini-slots containing one or more symbols. In someinstances, a symbol of a mini-slot or a mini-slot may be the smallestunit of scheduling. Each symbol may vary in duration depending on thesubcarrier spacing or frequency band of operation, for example. Further,some wireless communications systems may implement slot aggregation inwhich multiple slots or mini-slots are aggregated together and used forcommunication between a UE 115 and a base station 105.

The term “carrier” refers to a set of radio frequency spectrum resourceshaving a defined physical layer structure for supporting communicationsover a communication link 125. For example, a carrier of a communicationlink 125 may include a portion of a radio frequency spectrum band thatis operated according to physical layer channels for a given radioaccess technology. Each physical layer channel may carry user data,control information, or other signaling. A carrier may be associatedwith a pre-defined frequency channel (e.g., an E-UTRA absolute radiofrequency channel number (EARFCN)), and may be positioned according to achannel raster for discovery by UEs 115. Carriers may be downlink oruplink (e.g., in an FDD mode), or be configured to carry downlink anduplink communications (e.g., in a TDD mode). In some examples, signalwaveforms transmitted over a carrier may be made up of multiplesub-carriers (e.g., using multi-carrier modulation (MCM) techniques suchas OFDM or DFT-s-OFDM).

The organizational structure of the carriers may be different fordifferent radio access technologies (e.g., LTE, LTE-A, LTE-A Pro, NR,etc.). For example, communications over a carrier may be organizedaccording to TTIs or slots, each of which may include user data as wellas control information or signaling to support decoding the user data. Acarrier may also include dedicated acquisition signaling (e.g.,synchronization signals or system information, etc.) and controlsignaling that coordinates operation for the carrier. In some examples(e.g., in a carrier aggregation configuration), a carrier may also haveacquisition signaling or control signaling that coordinates operationsfor other carriers.

Physical channels may be multiplexed on a carrier according to varioustechniques. A physical control channel and a physical data channel maybe multiplexed on a downlink carrier, for example, using time divisionmultiplexing (TDM) techniques, frequency division multiplexing (FDM)techniques, or hybrid TDM-FDM techniques. In some examples, controlinformation transmitted in a physical control channel may be distributedbetween different control regions in a cascaded manner (e.g., between acommon control region or common search space and one or more UE-specificcontrol regions or UE-specific search spaces).

A carrier may be associated with a particular bandwidth of the radiofrequency spectrum, and in some examples the carrier bandwidth may bereferred to as a “system bandwidth” of the carrier or the wirelesscommunications system 100. For example, the carrier bandwidth may be oneof a number of predetermined bandwidths for carriers of a particularradio access technology (e.g., 1.4, 3, 5, 10, 15, 20, 40, or 80 MHz). Insome examples, each served UE 115 may be configured for operating overportions or all of the carrier bandwidth. In other examples, some UEs115 may be configured for operation using a narrowband protocol typethat is associated with a predefined portion or range (e.g., set ofsubcarriers or RBs) within a carrier (e.g., “in-band” deployment of anarrowband protocol type).

In a system employing MCM techniques, a resource element may consist ofone symbol period (e.g., a duration of one modulation symbol) and onesubcarrier, where the symbol period and subcarrier spacing are inverselyrelated. The number of bits carried by each resource element may dependon the modulation scheme (e.g., the order of the modulation scheme).Thus, the more resource elements that a UE 115 receives and the higherthe order of the modulation scheme, the higher the data rate may be forthe UE 115. In MIMO systems, a wireless communications resource mayrefer to a combination of a radio frequency spectrum resource, a timeresource, and a spatial resource (e.g., spatial layers), and the use ofmultiple spatial layers may further increase the data rate forcommunications with a UE 115.

Devices of the wireless communications system 100 (e.g., base stations105 or UEs 115) may have a hardware configuration that supportscommunications over a particular carrier bandwidth, or may beconfigurable to support communications over one of a set of carrierbandwidths. In some examples, the wireless communications system 100 mayinclude base stations 105 and/or UEs 115 that can support simultaneouscommunications via carriers associated with more than one differentcarrier bandwidth.

Wireless communications system 100 may support communication with a UE115 on multiple cells or carriers, a feature which may be referred to ascarrier aggregation (CA) or multi-carrier operation. A UE 115 may beconfigured with multiple downlink CCs and one or more uplink CCsaccording to a carrier aggregation configuration. Carrier aggregationmay be used with both FDD and TDD component carriers.

In some cases, wireless communications system 100 may utilize enhancedcomponent carriers (eCCs). An eCC may be characterized by one or morefeatures including wider carrier or frequency channel bandwidth, shortersymbol duration, shorter TTI duration, or modified control channelconfiguration. In some cases, an eCC may be associated with a carrieraggregation configuration or a dual connectivity configuration (e.g.,when multiple serving cells have a suboptimal or non-ideal backhaullink). An eCC may also be configured for use in unlicensed spectrum orshared spectrum (e.g., where more than one operator is allowed to usethe spectrum). An eCC characterized by wide carrier bandwidth mayinclude one or more segments that may be utilized by UEs 115 that arenot capable of monitoring the whole carrier bandwidth or are otherwiseconfigured to use a limited carrier bandwidth (e.g., to conserve power).

In some cases, an eCC may utilize a different symbol duration than otherCCs, which may include use of a reduced symbol duration as compared withsymbol durations of the other CCs. A shorter symbol duration may beassociated with increased spacing between adjacent subcarriers. Adevice, such as a UE 115 or base station 105, utilizing eCCs maytransmit wideband signals (e.g., according to frequency channel orcarrier bandwidths of 20, 40, 60, 80 MHz, etc.) at reduced symboldurations (e.g., 16.67 microseconds). A TTI in eCC may consist of one ormultiple symbol periods. In some cases, the TTI duration (that is, thenumber of symbol periods in a TTI) may be variable.

Wireless communications systems such as an NR system may utilize anycombination of licensed, shared, and unlicensed spectrum bands, amongothers. The flexibility of eCC symbol duration and subcarrier spacingmay allow for the use of eCC across multiple spectrums. In someexamples, NR shared spectrum may increase spectrum utilization andspectral efficiency, specifically through dynamic vertical (e.g., acrossthe frequency domain) and horizontal (e.g., across the time domain)sharing of resources.

A UE 115, which may be operating in an idle mode, may transmit a requestmessage to a base station 105. For example, the request message may befor system information. The base station 105 may transmit a responsemessage in response to the request message. The base station 105 mayinclude a random access response payload in a PDCCH signal withoutscheduling a PDSCH signal as part of a response message. In some cases,the base station may use the preamble index corresponding to the requestmessage to determine a modified RNTI. The base station may scramble aCRC of the response message with the modified RNTI. Additionally, oralternatively, the RAPID may be included in the PDCCH payload. In somecases, the base station may indicate the presence of the RAPID in thePDCCH payload based on a value of a frequency assignment field.

FIG. 2 illustrates an example of a wireless communications system 200 inaccordance with aspects of the present disclosure. In some examples,wireless communications system 200 may implement aspects of wirelesscommunications system 100. Wireless communications system 200 mayinclude UE 115-a and base station 105-a. UE 115-a may be an example of aUE 115 and base station 105-a may be an example of a base station 105 asdescribed herein.

Base station 105-a may periodically transmit a synchronization signalblock (SSB) 205 which includes some system information in a masterinformation block (MIB). The MIB may be transmitted in a physicalbroadcast channel (PBCH) in the SSB 205. A UE 115 which wakes up in thecell provided by base station 105-a or a UE 115 which performs initialaccess to base station 105-a may use the information in the MIB toreceive system information blocks (SIBs) carrying system information.System information may relate basic information for UEs 115 in thewireless communications system 200. There may be multiple different SIBmessages transmitted by base station 105-a, each of which may includedifferent system information. For example, a first SIB (e.g., SIB1) mayinclude a physical random access channel (PRACH) configuration andscheduling information for subsequent SIBs. The subsequent SIBs mayinclude information related to common channels, re-selectioninformation, etc. Base station 105-a may periodically transmit the SIBs,as base station 105-a may have to provide the system information tonewly served UEs 115 which wake up or arrive (e.g., from neighboringcells) in the cell provided by base station 105-a. In some cases,however, base station 105-a may stop periodically transmitting some ofthe SIBs. For example, if little UE mobility is detected, base station105-a may stop transmitting some of the SIBs (e.g., SIBs other thanSIB1) to reduce network energy usage and improve spectral efficiency.

UE 115-a may operate in an idle mode to conserve power usage. However,while operating in idle mode, UE 115-a may lose some configurations forthe wireless communications system 200. For example, UE 115-a may losethe system information, or the system information may have been updatedwhile UE 115-a was in idle mode.

UE 115-a may wake up and monitor for the SSB 205, which is periodicallytransmitted by base station 105-a. UE 115-a may receive a MIB andattempt to decode a SIB based on information included in the MIB. UE115-a may receive a first SIB (e.g., SIB1) including a PRACHconfiguration. However, base station 105-a may have identified little UEmobility while UE 115-a was operating in idle mode, and the other SIBsmay not be periodically transmitted. The first SIB may includeinformation related to an availability of an on-demand SI requestprocedure, which UE 115-a may follow if the other SIBs are notperiodically transmitted.

UE 115-a may transmit a request message 210 to base station 105-a. Basedon the PRACH configuration in SIB1, UE 115-a may identify some PRACHsequences to use in the request message 210 to request other SIBs. Therequest message may include a preamble, such as a PRACH preamble,associated with the system information being requested. In some cases,the request message 210 may be referred to as “MSG1.”

Base station 105-a may receive the request message 210 and generate aresponse message 220 to transmit in response. In some cases, theresponse message 220 may be an example of a “MSG2” or a random accessresponse. The response message 220 may include a random access preambleidentifier (RAPID) 215 which indicates the preamble used by UE 115-a torequest system information. UE 115-a may receive the response message220, determine the RAPID corresponds to the preamble included in therequest message 210, and determine the response message 220 is intendedfor UE 115-a.

In some cases, the response message 220 may include a PDCCH message anda PDSCH message, where the PDCCH message schedules the PDSCH message.The PDSCH message may include a special MAC sub-protocol data unit(PDU), where each sub-PDU includes just a MAC sub-header and a RAPID(not shown). In this example, a PDSCH structure for the PDSCH message inthe response message 220 may be the same as a MSG2 in response to aninitial access request from a UE 115. The response to initial accessrequest may include timing information, grants, etc., which may occupyresources of the PDSCH message, but the PDSCH message in the responsemessage 220 may just include a MAC sub-header and a RAPID.

In some cases, base station 105-a may receive a request message 210 frommultiple UEs 115. If base station 105-a receives a request message 210from multiple UEs 115, the PDSCH message may include a special MACsub-PDUs for each of the multiple UEs 115. However, if base station105-a just receives a request message 210 from one UE 115, base station105-a may still schedule a PDSCH message, which has a large amount ofoverhead, just to transmit a single MAC sub-header and a single RAPID.UE 115-a and base station 105-a may instead implement techniques toreduce the overhead for response messages to idle mode requests.

For example, base station 105-a may instead include a random accessresponse payload as downlink control information in a PDCCH message.Thus, if base station 105-a only has one random access response totransmit, base station 105-a may transmit the response message 220 usinga PDCCH message, and base station 105-a may not schedule a PDSCH messageas part of the response message 220.

In a first example, shown by the response message 220-a, base station105-a may use the RAPID 215 to determine the RNTI (e.g., a new ormodified RNTI). Base station 105-a may scramble a CRC 230-a of responsemessage 220-a with the modified RNTI. Therefore, the RAPID 215 may beincluded in the CRC 230. As shown, response message 220-a includes PDCCHpayload 225-a and CRC 230-a. The RAPID 215 may be included in the CRC230-a by scrambling the CRC 230-a with a modified RNTI.

In the first example, the modified RNTI may be determined based on aslot index, symbol index, frequency index, carrier ID, and preamble ofthe PRACH of the corresponding request message 210 and the RAPID 215, orany combination thereof. Therefore, the modified RNTI may be determinedbased on the resource allocation and preamble index (e.g., the RAPID215) of the corresponding PRACH message (e.g., MSG1 or the requestmessage 210). In some cases, base station 105-a may use a bitfieldpattern to distinguish the modified RNTI from previous, other RA-RNTIs.For example, a modified RNTI may have a different range of values fromother RA-RANTIs. If other RA-RNTI values range from, for example, “0000”through “FFEF,” a modified RNTI, which may be determined based on theRAPID 215, may have a value range from “FFF0” through “FFFF.” Some ofvalues may be reserved for other purposes, for example, FFFF may be usedto indicate SI-RNTI and FFFE may be used to indicate P-RNTI. In someimplementations, values reserved for other purposes may not be used toindicate a modified RNTI.

In some cases of the first example, the RAPID 215 may not be included inthe PDCCH payload 225-a. In some other examples, a portion of the RAPID215 may be used to generate the modified RNTI and included in the CRC230-a, and a remaining portion of the RAPID 215 may be included in thePDCCH payload 225-a. For example, if the RAPID 215 is 6 bits long, basestation 105-a may use 4 bits of the RAPID 215 to generate the modifiedRNTI and include the remaining 2 bits of the RAPID 215 in the PDCCHpayload 225-a. Other distributions of the RAPID 215 between the modifiedRNTI and the PDCCH payload 225-a may be used as well. In some cases, byusing a modified RNTI, base station 105-a may define a new payloadformat. In some cases, base station 105-a may include the RAPID 215(e.g., all bits of the RAPID 215) in both the modified RNTI and thePDCCH payload 225-a.

In a second example, shown by the response message 220-b, the RAPID 215may be included in the PDCCH payload 225. For example, the RAPID 215 isincluded in the PDCCH payload 225-b of the response message 220-b. Insome cases, of the second example, the CRC 230-b may be scrambled by aconventional RNTI such as RA-RNTI (e.g., not a modified RNTI asdescribed above). The RAPID 215 may correspond to the preamble indexused to transmit the request message 210, where the response message220-b is transmitted in response to the request message 210. Thus, theRAPID 215 may correspond to a preamble which UE 115-a used, and theRAPID 215 may not correspond to an instruction of which preamble indexUE 115-a should use (e.g., for a following PRACH message).

In some cases, base station 105-a may indicate the presence of the RAPID215 in the PDCCH payload 225-b based on a value of a frequencyassignment field. The PDCCH message (e.g., the response message 220) mayhave a DCI format normally used to schedule a PDSCH. Therefore, if afrequency assignment field is set to a special value, this may be anindication to the receiving UE 115 (e.g., UE 115-a) that the PDCCHmessage may be used for purposes other than to schedule PDSCH. Forexample, if the frequency assignment field is six bits long and set to“111111” or “111110,” it may be an indication that the RAPID 215 isincluded in the PDCCH payload 225-b. Additionally, or alternatively,base station 105-a may indicate the RAPID 215 is in the PDCCH payload225-b based on one or more reserved bits. For example, the frequencyassignment field may be set to “111111,” and a reserved bit may betoggled, which may indicate the RAPID 215 is included in the PDCCHpayload 225-b.

In some cases, multiple base stations 105 may coordinate, such that eachbase station 105 transmits a single random access response in caseswhere multiple request messages 210 are received. For example, if basestation 105-a receives two request messages 210, base station 105-a maysend one of the request messages to another base station 105. Then, basestation 105-a may transmit a response message 220 using just a PDCCHmessage and the other base station 105 may transmit a response message220 using just a PDCCH message, and neither base station 105 uses PDSCHresources for transmitting a response message.

The techniques described herein may be used for other idle moderequests. For example, UE 115-a and base station 105-a may implementsimilar techniques to handle an idle mode request for a downlink oruplink PRS. The PDCCH payload 225 may also include other parametersrelated to the PRS configuration. By using a modified RNTI, base station105-a may define a new payload format and use remaining available bitsin the PDCCH payload 225 for the PRS configuration. In some cases, eachidle mode request type may be associated with a type ID field in amodified RNTI.

FIG. 3 illustrates an example of a process flow 300 in accordance withaspects of the present disclosure. In some examples, process flow 300may implement aspects of wireless communications system 100. UE 115-bmay be an example of a UE 115 and base station 105-b may be an exampleof a base station 105 as described herein.

UE 115-b may be in an idle mode. UE 115-b may not have up-to-date systeminformation and may scan for an SSB from base station 105-b. At 305,base station 105-b may transmit the SSB. The SSB may include a MIB,which UE 115-b may use to decode a SIB as described in FIG. 2 . The SIBmay be an example of a SIB1, which includes a PRACH configuration for UE115-b. UE 115-b may determine that base station 105-b is notperiodically transmitting other SIBs based on the information receivedfrom the SSB.

At 310, UE 115-b may transmit a request message to base station 105-bwhile operating in the idle mode. In some cases, the request message maybe a system information request. UE 115-b may transmit the requestmessage with a preamble corresponding to requested system information.UE 115-b may identify some PRACH preambles based on the information inSIB 1. In some other examples, the request message may be a PRS request.In some cases, the PRS request may be a request for the base station105-b to transmit DL PRS or a request to allow UE 115-b to transmit ULPRS.

At 315, base station 105-b may generate, in response to the requestmessage, a response message including a random access preamble indexcorresponding to the received request message. As described in FIG. 2 ,base station 105-b may transmit the response message as downlink controlinformation in a PDCCH signal and not use a PDSCH signal. Therefore,base station 105-b may implement techniques to transmit the responsemessage in the PDCCH signal. Base station 105-b may also includeindications that the response message is conveyed using the PDCCHsignal, such that UE 115-b may identify the information in the responsemessage.

For example, base station 105-b may determine a RNTI based on the randomaccess preamble index and scramble a CRC of the generated responsemessage with the determined RNTI. Base station 105-b may set a bit fieldpattern of the generated response message indicating the RNTI iscalculated based on the random access preamble index. In some cases,base station 105-b may include a first subset of bits of the randomaccess preamble index in the RNTI and include a second subset of bits ofthe random access preamble index in a payload of the generated responsemessage. These examples may relate to the first example described inFIG. 2 .

In another example, base station 105-b may determine a payload for thegenerated response message including the random access preamble index.In some cases, base station 105-b may indicate the payload for thegenerated response message includes the random access preamble indexbased on a value of a frequency assignment bit field. For example, basestation 105-b may set a value of the frequency assignment bit field suchthat UE 115-b can determine that the PDCCH signal carries the randomaccess preamble index and is not used for scheduling a PDSCH.Additionally, or alternatively, the base station may indicate thepayload includes the random access preamble index is further based atleast in part on one or more reserved bits of the generated responsemessage. These examples may relate to the second example described inFIG. 2 .

At 320, UE 115-b may monitor a physical downlink control channel for aresponse message to the request message, the response message includingthe random access preamble index associated with the request message. At325, base station 105-b may transmit the generated response message onthe physical downlink control channel, and UE 115-b may receive theresponse message.

The received response message may be an acknowledgment of the requestmessage. In some cases, the received response message may includeinformation in response to the request message. For example, the requestmessage may be a system information request and the information inresponse to the request message may include timing or frequencyinformation related to when a requested system information will betransmitted. In some examples, the request message may be a PRS request,and the information in response to the request message may include aconfiguration for a PRS to be transmitted in response to the request. Insome cases, a type of the response message may be indicated by atype-identifying field in the RNTI. In some cases, the response messagemay include a single random access response.

FIG. 4 shows a block diagram 400 of a device 405 in accordance withaspects of the present disclosure. The device 405 may be an example ofaspects of a UE 115 as described herein. The device 405 may include areceiver 410, a communications manager 415, and a transmitter 420. Thedevice 405 may also include a processor. Each of these components may bein communication with one another (e.g., via one or more buses).

The receiver 410 may receive information such as packets, user data, orcontrol information associated with various information channels (e.g.,control channels, data channels, and information related to the presentdisclosure, etc.). Information may be passed on to other components ofthe device 405. The receiver 410 may be an example of aspects of thetransceiver 720 described with reference to FIG. 7 . The receiver 410may utilize a single antenna or a set of antennas.

The communications manager 415 may transmit a request message to a basestation while operating in an idle mode, monitor a physical downlinkcontrol channel for a response message to the request message, theresponse message including a random access preamble index associatedwith the request message, and receive the response message on thephysical downlink control channel. The communications manager 415 may bean example of aspects of the communications manager 710 describedherein.

The communications manager 415, or its sub-components, may beimplemented in hardware, code (e.g., software or firmware) executed by aprocessor, or any combination thereof. If implemented in code executedby a processor, the functions of the communications manager 415, or itssub-components may be executed by a general-purpose processor, a DSP, anapplication-specific integrated circuit (ASIC), an FPGA or otherprogrammable logic device, discrete gate or transistor logic, discretehardware components, or any combination thereof designed to perform thefunctions described in the present disclosure.

The communications manager 415, or its sub-components, may be physicallylocated at various positions, including being distributed such thatportions of functions are implemented at different physical locations byone or more physical components. In some examples, the communicationsmanager 415, or its sub-components, may be a separate and distinctcomponent in accordance with various aspects of the present disclosure.In some examples, the communications manager 415, or its sub-components,may be combined with one or more other hardware components, includingbut not limited to an input/output (I/O) component, a transceiver, anetwork server, another computing device, one or more other componentsdescribed in the present disclosure, or a combination thereof inaccordance with various aspects of the present disclosure.

The transmitter 420 may transmit signals generated by other componentsof the device 405. In some examples, the transmitter 420 may becollocated with a receiver 410 in a transceiver module. For example, thetransmitter 420 may be an example of aspects of the transceiver 720described with reference to FIG. 7 . The transmitter 420 may utilize asingle antenna or a set of antennas.

FIG. 5 shows a block diagram 500 of a device 505 in accordance withaspects of the present disclosure. The device 505 may be an example ofaspects of a device 405 or a UE 115 as described herein. The device 505may include a receiver 510, a communications manager 515, and atransmitter 535. The device 505 may also include a processor. Each ofthese components may be in communication with one another (e.g., via oneor more buses).

The receiver 510 may receive information such as packets, user data, orcontrol information associated with various information channels (e.g.,control channels, data channels, and information related to the presentdisclosure, etc.). Information may be passed on to other components ofthe device 505. The receiver 510 may be an example of aspects of thetransceiver 720 described with reference to FIG. 7 . The receiver 510may utilize a single antenna or a set of antennas.

The communications manager 515 may be an example of aspects of thecommunications manager 415 as described herein. The communicationsmanager 515 may include a request message component 520, a monitoringcomponent 525, and a response message component 530. The communicationsmanager 515 may be an example of aspects of the communications manager710 described herein.

The request message component 520 may transmit a request message to abase station while operating in an idle mode. The monitoring component525 may monitor a physical downlink control channel for a responsemessage to the request message, the response message including a randomaccess preamble index associated with the request message. The responsemessage component 530 may receive the response message on the physicaldownlink control channel.

The transmitter 535 may transmit signals generated by other componentsof the device 505. In some examples, the transmitter 535 may becollocated with a receiver 510 in a transceiver module. For example, thetransmitter 535 may be an example of aspects of the transceiver 720described with reference to FIG. 7 . The transmitter 535 may utilize asingle antenna or a set of antennas.

FIG. 6 shows a block diagram 600 of a communications manager 605 inaccordance with aspects of the present disclosure. The communicationsmanager 605 may be an example of aspects of a communications manager415, a communications manager 515, or a communications manager 710described herein. The communications manager 605 may include a requestmessage component 610, a monitoring component 615, a response messagecomponent 620, a RNTI component 625, and a payload identifying component630. Each of these modules may communicate, directly or indirectly, withone another (e.g., via one or more buses).

The request message component 610 may transmit a request message to abase station while operating in an idle mode. In some cases, a receivedresponse message includes information in response to the requestmessage. In some cases, the request message is a system informationrequest and the information in response to the request message includestiming or frequency information related to when a requested systeminformation will be transmitted. In some cases, the request message is aPRS request, and the information in response to the request messageincludes a configuration for a PRS to be transmitted in response to therequest.

The monitoring component 615 may monitor a physical downlink controlchannel for a response message to the request message, the responsemessage including a random access preamble index associated with therequest message. In some cases, the response message includes a singlerandom access response. In some examples, the monitoring component 615may monitor for the received response message on the physical downlinkcontrol channel based on the response message including a single randomaccess response.

The response message component 620 may receive the response message onthe physical downlink control channel. In some cases, the receivedresponse message is an acknowledgment of the request message. In somecases, a type of the received response message is indicated by atype-identifying field in an RNTI.

The RNTI component 625 may determine an RNTI based on the random accesspreamble index. In some examples, the RNTI component 625 may unscramblea CRC of the response message with the RNTI. In some examples, the RNTIcomponent 625 may identify a bit field pattern indicating the RNTI forthe response message is calculated based on the random access preambleindex.

In some examples, the RNTI component 625 may identify a first subset ofbits of the random access preamble index in the RNTI. The payloadidentifying component 630 may identify a second subset of bits of therandom access preamble index in a payload of the response message.

In some examples, the payload identifying component 630 may identify therandom access preamble index in a payload of the response message. Insome examples, the payload identifying component 630 may identify apayload of the response message based on a value of a frequencyassignment bit field of the response message. In some cases, the payloadis further identified based on one or more reserved bits of the responsemessage.

FIG. 7 shows a diagram of a system 700 including a device 705 inaccordance with aspects of the present disclosure. The device 705 may bean example of or include the components of device 405, device 505, or aUE 115 as described herein. The device 705 may include components forbi-directional voice and data communications including components fortransmitting and receiving communications, including a communicationsmanager 710, an I/O controller 715, a transceiver 720, an antenna 725,memory 730, and a processor 740. These components may be in electroniccommunication via one or more buses (e.g., bus 745).

The communications manager 710 may transmit a request message to a basestation while operating in an idle mode, monitor a physical downlinkcontrol channel for a response message to the request message, theresponse message including a random access preamble index associatedwith the request message, and receive the response message on thephysical downlink control channel.

The I/O controller 715 may manage input and output signals for thedevice 705. The I/O controller 715 may also manage peripherals notintegrated into the device 705. In some cases, the I/O controller 715may represent a physical connection or port to an external peripheral.In some cases, the I/O controller 715 may utilize an operating systemsuch as iOS®, ANDROID®, MS-DOS®, MS-WINDOWS®, OS/2®, UNIX®, LINUX®, oranother known operating system. In other cases, the I/O controller 715may represent or interact with a modem, a keyboard, a mouse, atouchscreen, or a similar device. In some cases, the I/O controller 715may be implemented as part of a processor. In some cases, a user mayinteract with the device 705 via the I/O controller 715 or via hardwarecomponents controlled by the I/O controller 715.

The transceiver 720 may communicate bi-directionally, via one or moreantennas, wired, or wireless links as described above. For example, thetransceiver 720 may represent a wireless transceiver and may communicatebi-directionally with another wireless transceiver. The transceiver 720may also include a modem to modulate the packets and provide themodulated packets to the antennas for transmission, and to demodulatepackets received from the antennas.

In some cases, the wireless device may include a single antenna 725.However, in some cases the device may have more than one antenna 725,which may be capable of concurrently transmitting or receiving multiplewireless transmissions.

The memory 730 may include RAM and ROM. The memory 730 may storecomputer-readable, computer-executable code 735 including instructionsthat, when executed, cause the processor to perform various functionsdescribed herein. In some cases, the memory 730 may contain, among otherthings, a BIOS which may control basic hardware or software operationsuch as the interaction with peripheral components or devices.

The processor 740 may include an intelligent hardware device, (e.g., ageneral-purpose processor, a DSP, a CPU, a microcontroller, an ASIC, anFPGA, a programmable logic device, a discrete gate or transistor logiccomponent, a discrete hardware component, or any combination thereof).In some cases, the processor 740 may be configured to operate a memoryarray using a memory controller. In other cases, a memory controller maybe integrated into the processor 740. The processor 740 may beconfigured to execute computer-readable instructions stored in a memory(e.g., the memory 730) to cause the device 705 to perform variousfunctions (e.g., functions or tasks supporting downlink controlinformation response to idle mode requests).

The code 735 may include instructions to implement aspects of thepresent disclosure, including instructions to support wirelesscommunications. The code 735 may be stored in a non-transitorycomputer-readable medium such as system memory or other type of memory.In some cases, the code 735 may not be directly executable by theprocessor 740 but may cause a computer (e.g., when compiled andexecuted) to perform functions described herein.

FIG. 8 shows a block diagram 800 of a device 805 in accordance withaspects of the present disclosure. The device 805 may be an example ofaspects of a base station 105 as described herein. The device 805 mayinclude a receiver 810, a communications manager 815, and a transmitter820. The device 805 may also include a processor. Each of thesecomponents may be in communication with one another (e.g., via one ormore buses).

The receiver 810 may receive information such as packets, user data, orcontrol information associated with various information channels (e.g.,control channels, data channels, and information related to the presentdisclosure, etc.). Information may be passed on to other components ofthe device 805. The receiver 810 may be an example of aspects of thetransceiver 1120 described with reference to FIG. 11 . The receiver 810may utilize a single antenna or a set of antennas.

The communications manager 815 may receive a request message from a UEoperating in an idle mode, generate, in response to the request message,a response message including a random access preamble indexcorresponding to the received request message, and transmit thegenerated response message on a physical downlink control channel. Thecommunications manager 815 may be an example of aspects of thecommunications manager 1110 described herein.

The communications manager 815, or its sub-components, may beimplemented in hardware, code (e.g., software or firmware) executed by aprocessor, or any combination thereof. If implemented in code executedby a processor, the functions of the communications manager 815, or itssub-components may be executed by a general-purpose processor, a DSP, anapplication-specific integrated circuit (ASIC), an FPGA or otherprogrammable logic device, discrete gate or transistor logic, discretehardware components, or any combination thereof designed to perform thefunctions described in the present disclosure.

The communications manager 815, or its sub-components, may be physicallylocated at various positions, including being distributed such thatportions of functions are implemented at different physical locations byone or more physical components. In some examples, the communicationsmanager 815, or its sub-components, may be a separate and distinctcomponent in accordance with various aspects of the present disclosure.In some examples, the communications manager 815, or its sub-components,may be combined with one or more other hardware components, includingbut not limited to an input/output (I/O) component, a transceiver, anetwork server, another computing device, one or more other componentsdescribed in the present disclosure, or a combination thereof inaccordance with various aspects of the present disclosure.

The transmitter 820 may transmit signals generated by other componentsof the device 805. In some examples, the transmitter 820 may becollocated with a receiver 810 in a transceiver module. For example, thetransmitter 820 may be an example of aspects of the transceiver 1120described with reference to FIG. 11 . The transmitter 820 may utilize asingle antenna or a set of antennas.

FIG. 9 shows a block diagram 900 of a device 905 in accordance withaspects of the present disclosure. The device 905 may be an example ofaspects of a device 805 or a base station 105 as described herein. Thedevice 905 may include a receiver 910, a communications manager 915, anda transmitter 935. The device 905 may also include a processor. Each ofthese components may be in communication with one another (e.g., via oneor more buses).

The receiver 910 may receive information such as packets, user data, orcontrol information associated with various information channels (e.g.,control channels, data channels, and information related to the presentdisclosure, etc.). Information may be passed on to other components ofthe device 905. The receiver 910 may be an example of aspects of thetransceiver 1120 described with reference to FIG. 11 . The receiver 910may utilize a single antenna or a set of antennas.

The communications manager 915 may be an example of aspects of thecommunications manager 815 as described herein. The communicationsmanager 915 may include a request message component 920, a responsemessage generating component 925, and a response message transmittingcomponent 930. The communications manager 915 may be an example ofaspects of the communications manager 1110 described herein.

The request message component 920 may receive a request message from aUE operating in an idle mode. The response message generating component925 may generate, in response to the request message, a response messageincluding a random access preamble index corresponding to the receivedrequest message. The response message transmitting component 930 maytransmit the generated response message on a physical downlink controlchannel.

The transmitter 935 may transmit signals generated by other componentsof the device 905. In some examples, the transmitter 935 may becollocated with a receiver 910 in a transceiver module. For example, thetransmitter 935 may be an example of aspects of the transceiver 1120described with reference to FIG. 11 . The transmitter 935 may utilize asingle antenna or a set of antennas.

FIG. 10 shows a block diagram 1000 of a communications manager 1005 inaccordance with aspects of the present disclosure. The communicationsmanager 1005 may be an example of aspects of a communications manager815, a communications manager 915, or a communications manager 1110described herein. The communications manager 1005 may include a requestmessage component 1010, a response message generating component 1015, aresponse message transmitting component 1020, a RNTI component 1025, anda payload component 1030. Each of these modules may communicate,directly or indirectly, with one another (e.g., via one or more buses).

The request message component 1010 may receive a request message from aUE operating in an idle mode. In some cases, a generated responsemessage includes information in response to the request message. In somecases, the request message is a system information request and theinformation in response to the request message includes timing orfrequency information related to when a requested system informationwill be transmitted. In some cases, the request message is a PRSrequest, and the information in response to the request message includesa configuration for a PRS to be transmitted in response to the request.

The response message generating component 1015 may generate, in responseto the request message, a response message including a random accesspreamble index corresponding to the received request message. In somecases, the generated response message is an acknowledgment of therequest message. In some cases, a type of the generated response messageis indicated by a type-identifying field in the RNTI.

The response message transmitting component 1020 may transmit thegenerated response message on a physical downlink control channel. Insome examples, the response message transmitting component 1020 mayidentify a single random access response for the response message, wherethe generated response message is transmitted on the physical downlinkcontrol channel based on the identifying.

The RNTI component 1025 may determine the RNTI based on the randomaccess preamble index. In some examples, the RNTI component 1025 mayscramble a CRC of the generated response message with the determinedRNTI. In some examples, the RNTI component 1025 may set a bit fieldpattern of the generated response message indicating the RNTI iscalculated based on the random access preamble index.

In some examples, the RNTI component 1025 may include a first subset ofbits of the random access preamble index in the RNTI. The payloadcomponent 1030 may include a second subset of bits of the random accesspreamble index in a payload of the generated response message.

In some examples, the payload component 1030 may determine a payload forthe generated response message including the random access preambleindex. In some examples, indicating a payload for the generated responsemessage includes the random access preamble index based on a value of afrequency assignment bit field. In some examples, indicating the payloadincludes the random access preamble index is further based on one ormore reserved bits of the generated response message.

FIG. 11 shows a diagram of a system 1100 including a device 1105 inaccordance with aspects of the present disclosure. The device 1105 maybe an example of or include the components of device 805, device 905, ora base station 105 as described herein. The device 1105 may includecomponents for bi-directional voice and data communications includingcomponents for transmitting and receiving communications, including acommunications manager 1110, a network communications manager 1115, atransceiver 1120, an antenna 1125, memory 1130, a processor 1140, and aninter-station communications manager 1145. These components may be inelectronic communication via one or more buses (e.g., bus 1150).

The communications manager 1110 may receive a request message from a UEoperating in an idle mode, generate, in response to the request message,a response message including a random access preamble indexcorresponding to the received request message, and transmit thegenerated response message on a physical downlink control channel.

The network communications manager 1115 may manage communications withthe core network (e.g., via one or more wired backhaul links). Forexample, the network communications manager 1115 may manage the transferof data communications for client devices, such as one or more UEs 115.

The transceiver 1120 may communicate bi-directionally, via one or moreantennas, wired, or wireless links as described above. For example, thetransceiver 1120 may represent a wireless transceiver and maycommunicate bi-directionally with another wireless transceiver. Thetransceiver 1120 may also include a modem to modulate the packets andprovide the modulated packets to the antennas for transmission, and todemodulate packets received from the antennas.

In some cases, the wireless device may include a single antenna 1125.However, in some cases the device may have more than one antenna 1125,which may be capable of concurrently transmitting or receiving multiplewireless transmissions.

The memory 1130 may include RAM, ROM, or a combination thereof. Thememory 1130 may store computer-readable code 1135 including instructionsthat, when executed by a processor (e.g., the processor 1140) cause thedevice to perform various functions described herein. In some cases, thememory 1130 may contain, among other things, a BIOS which may controlbasic hardware or software operation such as the interaction withperipheral components or devices.

The processor 1140 may include an intelligent hardware device, (e.g., ageneral-purpose processor, a DSP, a CPU, a microcontroller, an ASIC, anFPGA, a programmable logic device, a discrete gate or transistor logiccomponent, a discrete hardware component, or any combination thereof).In some cases, the processor 1140 may be configured to operate a memoryarray using a memory controller. In some cases, a memory controller maybe integrated into processor 1140. The processor 1140 may be configuredto execute computer-readable instructions stored in a memory (e.g., thememory 1130) to cause the device 1105 to perform various functions(e.g., functions or tasks supporting downlink control informationresponse to idle mode requests).

The inter-station communications manager 1145 may manage communicationswith other base station 105, and may include a controller or schedulerfor controlling communications with UEs 115 in cooperation with otherbase stations 105. For example, the inter-station communications manager1145 may coordinate scheduling for transmissions to UEs 115 for variousinterference mitigation techniques such as beamforming or jointtransmission. In some examples, the inter-station communications manager1145 may provide an X2 interface within an LTE/LTE-A wirelesscommunication network technology to provide communication between basestations 105.

The code 1135 may include instructions to implement aspects of thepresent disclosure, including instructions to support wirelesscommunications. The code 1135 may be stored in a non-transitorycomputer-readable medium such as system memory or other type of memory.In some cases, the code 1135 may not be directly executable by theprocessor 1140 but may cause a computer (e.g., when compiled andexecuted) to perform functions described herein.

FIG. 12 shows a flowchart illustrating a method 1200 in accordance withaspects of the present disclosure. The operations of method 1200 may beimplemented by a UE 115 or its components as described herein. Forexample, the operations of method 1200 may be performed by acommunications manager as described with reference to FIGS. 4 through 7. In some examples, a UE may execute a set of instructions to controlthe functional elements of the UE to perform the functions describedbelow. Additionally or alternatively, a UE may perform aspects of thefunctions described below using special-purpose hardware.

At 1205, the UE may transmit a request message to a base station whileoperating in an idle mode. The operations of 1205 may be performedaccording to the methods described herein. In some examples, aspects ofthe operations of 1205 may be performed by a request message componentas described with reference to FIGS. 4 through 7 .

At 1210, the UE may monitor a physical downlink control channel for aresponse message to the request message, the response message includinga random access preamble index associated with the request message. Theoperations of 1210 may be performed according to the methods describedherein. In some examples, aspects of the operations of 1210 may beperformed by a monitoring component as described with reference to FIGS.4 through 7 .

At 1215, the UE may receive the response message on the physicaldownlink control channel. The operations of 1215 may be performedaccording to the methods described herein. In some examples, aspects ofthe operations of 1215 may be performed by a response message componentas described with reference to FIGS. 4 through 7 .

FIG. 13 shows a flowchart illustrating a method 1300 in accordance withaspects of the present disclosure. The operations of method 1300 may beimplemented by a UE 115 or its components as described herein. Forexample, the operations of method 1300 may be performed by acommunications manager as described with reference to FIGS. 4 through 7. In some examples, a UE may execute a set of instructions to controlthe functional elements of the UE to perform the functions describedbelow. Additionally or alternatively, a UE may perform aspects of thefunctions described below using special-purpose hardware.

At 1305, the UE may transmit a request message to a base station whileoperating in an idle mode. The operations of 1305 may be performedaccording to the methods described herein. In some examples, aspects ofthe operations of 1305 may be performed by a request message componentas described with reference to FIGS. 4 through 7 .

At 1310, the UE may monitor a physical downlink control channel for aresponse message to the request message, the response message includinga random access preamble index associated with the request message. Theoperations of 1310 may be performed according to the methods describedherein. In some examples, aspects of the operations of 1310 may beperformed by a monitoring component as described with reference to FIGS.4 through 7 .

At 1315, the UE may determine the RNTI based on the random accesspreamble index. The operations of 1315 may be performed according to themethods described herein. In some examples, aspects of the operations of1315 may be performed by a RNTI component as described with reference toFIGS. 4 through 7 .

At 1320, the UE may receive the response message on the physicaldownlink control channel. The operations of 1320 may be performedaccording to the methods described herein. In some examples, aspects ofthe operations of 1320 may be performed by a response message componentas described with reference to FIGS. 4 through 7 .

At 1325, the UE may unscramble a CRC of the response message with theRNTI. The operations of 1325 may be performed according to the methodsdescribed herein. In some examples, aspects of the operations of 1325may be performed by a RNTI component as described with reference toFIGS. 4 through 7 .

FIG. 14 shows a flowchart illustrating a method 1400 in accordance withaspects of the present disclosure. The operations of method 1400 may beimplemented by a UE 115 or its components as described herein. Forexample, the operations of method 1400 may be performed by acommunications manager as described with reference to FIGS. 4 through 7. In some examples, a UE may execute a set of instructions to controlthe functional elements of the UE to perform the functions describedbelow. Additionally or alternatively, a UE may perform aspects of thefunctions described below using special-purpose hardware.

At 1405, the UE may transmit a request message to a base station whileoperating in an idle mode. The operations of 1405 may be performedaccording to the methods described herein. In some examples, aspects ofthe operations of 1405 may be performed by a request message componentas described with reference to FIGS. 4 through 7 .

At 1410, the UE may monitor a physical downlink control channel for aresponse message to the request message, the response message includinga random access preamble index associated with the request message. Theoperations of 1410 may be performed according to the methods describedherein. In some examples, aspects of the operations of 1410 may beperformed by a monitoring component as described with reference to FIGS.4 through 7 .

At 1415, the UE may receive the response message on the physicaldownlink control channel. The operations of 1415 may be performedaccording to the methods described herein. In some examples, aspects ofthe operations of 1415 may be performed by a response message componentas described with reference to FIGS. 4 through 7 .

At 1420, the UE may identify the random access preamble index in apayload of the response message. The operations of 1420 may be performedaccording to the methods described herein. In some examples, aspects ofthe operations of 1420 may be performed by a payload identifyingcomponent as described with reference to FIGS. 4 through 7 .

FIG. 15 shows a flowchart illustrating a method 1500 in accordance withaspects of the present disclosure. The operations of method 1500 may beimplemented by a base station 105 or its components as described herein.For example, the operations of method 1500 may be performed by acommunications manager as described with reference to FIGS. 8 through 11. In some examples, a base station may execute a set of instructions tocontrol the functional elements of the base station to perform thefunctions described below. Additionally or alternatively, a base stationmay perform aspects of the functions described below usingspecial-purpose hardware.

At 1505, the base station may receive a request message from a UEoperating in an idle mode. The operations of 1505 may be performedaccording to the methods described herein. In some examples, aspects ofthe operations of 1505 may be performed by a request message componentas described with reference to FIGS. 8 through 11 .

At 1510, the base station may generate, in response to the requestmessage, a response message including a random access preamble indexcorresponding to the received request message. The operations of 1510may be performed according to the methods described herein. In someexamples, aspects of the operations of 1510 may be performed by aresponse message generating component as described with reference toFIGS. 8 through 11 .

At 1515, the base station may transmit the generated response message ona physical downlink control channel. The operations of 1515 may beperformed according to the methods described herein. In some examples,aspects of the operations of 1515 may be performed by a response messagetransmitting component as described with reference to FIGS. 8 through 11.

FIG. 16 shows a flowchart illustrating a method 1600 in accordance withaspects of the present disclosure. The operations of method 1600 may beimplemented by a base station 105 or its components as described herein.For example, the operations of method 1600 may be performed by acommunications manager as described with reference to FIGS. 8 through 11. In some examples, a base station may execute a set of instructions tocontrol the functional elements of the base station to perform thefunctions described below. Additionally or alternatively, a base stationmay perform aspects of the functions described below usingspecial-purpose hardware.

At 1605, the base station may receive a request message from a UEoperating in an idle mode. The operations of 1605 may be performedaccording to the methods described herein. In some examples, aspects ofthe operations of 1605 may be performed by a request message componentas described with reference to FIGS. 8 through 11 .

At 1610, the base station may generate, in response to the requestmessage, a response message including a random access preamble indexcorresponding to the received request message. The operations of 1615may be performed according to the methods described herein. In someexamples, aspects of the operations of 1615 may be performed by aresponse message generating component as described with reference toFIGS. 8 through 11 .

At 1615, the base station may determine the RNTI based on the randomaccess preamble index. The operations of 1610 may be performed accordingto the methods described herein. In some examples, aspects of theoperations of 1610 may be performed by a RNTI component as describedwith reference to FIGS. 8 through 11 .

At 1620, the base station may scramble a CRC of the generated responsemessage with the determined RNTI. The operations of 1620 may beperformed according to the methods described herein. In some examples,aspects of the operations of 1620 may be performed by a RNTI componentas described with reference to FIGS. 8 through 11 .

At 1625, the base station may transmit the generated response message ona physical downlink control channel. The operations of 1625 may beperformed according to the methods described herein. In some examples,aspects of the operations of 1625 may be performed by a response messagetransmitting component as described with reference to FIGS. 8 through 11.

FIG. 17 shows a flowchart illustrating a method 1700 in accordance withaspects of the present disclosure. The operations of method 1700 may beimplemented by a base station 105 or its components as described herein.For example, the operations of method 1700 may be performed by acommunications manager as described with reference to FIGS. 8 through 11. In some examples, a base station may execute a set of instructions tocontrol the functional elements of the base station to perform thefunctions described below. Additionally or alternatively, a base stationmay perform aspects of the functions described below usingspecial-purpose hardware.

At 1705, the base station may receive a request message from a UEoperating in an idle mode. The operations of 1705 may be performedaccording to the methods described herein. In some examples, aspects ofthe operations of 1705 may be performed by a request message componentas described with reference to FIGS. 8 through 11 .

At 1710, the base station may generate, in response to the requestmessage, a response message including a random access preamble indexcorresponding to the received request message. The operations of 1715may be performed according to the methods described herein. In someexamples, aspects of the operations of 1715 may be performed by aresponse message generating component as described with reference toFIGS. 8 through 11 .

At 1715, the base station may determine a payload for the generatedresponse message including the random access preamble index. Theoperations of 1710 may be performed according to the methods describedherein. In some examples, aspects of the operations of 1710 may beperformed by a payload component as described with reference to FIGS. 8through 11 .

At 1720, the base station may transmit the generated response message ona physical downlink control channel. The operations of 1720 may beperformed according to the methods described herein. In some examples,aspects of the operations of 1720 may be performed by a response messagetransmitting component as described with reference to FIGS. 8 through 11.

It should be noted that the methods described above describe possibleimplementations, and that the operations and the steps may be rearrangedor otherwise modified and that other implementations are possible.Further, aspects from two or more of the methods may be combined.

Techniques described herein may be used for various wirelesscommunications systems such as code division multiple access (CDMA),time division multiple access (TDMA), frequency division multiple access(FDMA), orthogonal frequency division multiple access (OFDMA), singlecarrier frequency division multiple access (SC-FDMA), and other systems.A CDMA system may implement a radio technology such as CDMA2000,Universal Terrestrial Radio Access (UTRA), etc. CDMA2000 covers IS-2000,IS-95, and IS-856 standards. IS-2000 Releases may be commonly referredto as CDMA2000 1×, 1×, etc. IS-856 (TIA-856) is commonly referred to asCDMA2000 1×EV-DO, High Rate Packet Data (HRPD), etc. UTRA includesWideband CDMA (WCDMA) and other variants of CDMA. A TDMA system mayimplement a radio technology such as Global System for MobileCommunications (GSM).

An OFDMA system may implement a radio technology such as Ultra MobileBroadband (UMB), Evolved UTRA (E-UTRA), Institute of Electrical andElectronics Engineers (IEEE) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE802.20, Flash-OFDM, etc. UTRA and E-UTRA are part of Universal MobileTelecommunications System (UMTS). LTE, LTE-A, and LTE-A Pro are releasesof UMTS that use E-UTRA. UTRA, E-UTRA, UMTS, LTE, LTE-A, LTE-A Pro, NR,and GSM are described in documents from the organization named “3rdGeneration Partnership Project” (3GPP). CDMA2000 and UMB are describedin documents from an organization named “3rd Generation PartnershipProject 2” (3GPP2). The techniques described herein may be used for thesystems and radio technologies mentioned above as well as other systemsand radio technologies. While aspects of an LTE, LTE-A, LTE-A Pro, or NRsystem may be described for purposes of example, and LTE, LTE-A, LTE-APro, or NR terminology may be used in much of the description, thetechniques described herein are applicable beyond LTE, LTE-A, LTE-A Pro,or NR applications.

A macro cell generally covers a relatively large geographic area (e.g.,several kilometers in radius) and may allow unrestricted access by UEs115 with service subscriptions with the network provider. A small cellmay be associated with a lower-powered base station 105, as comparedwith a macro cell, and a small cell may operate in the same or different(e.g., licensed, unlicensed, etc.) frequency bands as macro cells. Smallcells may include pico cells, femto cells, and micro cells according tovarious examples. A pico cell, for example, may cover a small geographicarea and may allow unrestricted access by UEs 115 with servicesubscriptions with the network provider. A femto cell may also cover asmall geographic area (e.g., a home) and may provide restricted accessby UEs 115 having an association with the femto cell (e.g., UEs 115 in aclosed subscriber group (CSG), UEs 115 for users in the home, and thelike). An eNB for a macro cell may be referred to as a macro eNB. An eNBfor a small cell may be referred to as a small cell eNB, a pico eNB, afemto eNB, or a home eNB. An eNB may support one or multiple (e.g., two,three, four, and the like) cells, and may also support communicationsusing one or multiple component carriers.

The wireless communications system 100 or systems described herein maysupport synchronous or asynchronous operation. For synchronousoperation, the base stations 105 may have similar frame timing, andtransmissions from different base stations 105 may be approximatelyaligned in time. For asynchronous operation, the base stations 105 mayhave different frame timing, and transmissions from different basestations 105 may not be aligned in time. The techniques described hereinmay be used for either synchronous or asynchronous operations.

Information and signals described herein may be represented using any ofa variety of different technologies and techniques. For example, data,instructions, commands, information, signals, bits, symbols, and chipsthat may be referenced throughout the above description may berepresented by voltages, currents, electromagnetic waves, magneticfields or particles, optical fields or particles, or any combinationthereof.

The various illustrative blocks and modules described in connection withthe disclosure herein may be implemented or performed with ageneral-purpose processor, a digital signal processor (DSP), anapplication-specific integrated circuit (ASIC), a field-programmablegate array (FPGA) or other programmable logic device (PLD), discretegate or transistor logic, discrete hardware components, or anycombination thereof designed to perform the functions described herein.A general-purpose processor may be a microprocessor, but in thealternative, the processor may be any conventional processor,controller, microcontroller, or state machine. A processor may also beimplemented as a combination of computing devices (e.g., a combinationof a DSP and a microprocessor, multiple microprocessors, one or moremicroprocessors in conjunction with a DSP core, or any other suchconfiguration).

The functions described herein may be implemented in hardware, softwareexecuted by a processor, firmware, or any combination thereof. Ifimplemented in software executed by a processor, the functions may bestored on or transmitted over as one or more instructions or code on acomputer-readable medium. Other examples and implementations are withinthe scope of the disclosure and appended claims. For example, due to thenature of software, functions described above can be implemented usingsoftware executed by a processor, hardware, firmware, hardwiring, orcombinations of any of these. Features implementing functions may alsobe physically located at various positions, including being distributedsuch that portions of functions are implemented at different physicallocations.

Computer-readable media includes both non-transitory computer storagemedia and communication media including any medium that facilitatestransfer of a computer program from one place to another. Anon-transitory storage medium may be any available medium that can beaccessed by a general purpose or special purpose computer. By way ofexample, and not limitation, non-transitory computer-readable media mayinclude random-access memory (RAM), read-only memory (ROM), electricallyerasable programmable read only memory (EEPROM), flash memory, compactdisk (CD) ROM or other optical disk storage, magnetic disk storage orother magnetic storage devices, or any other non-transitory medium thatcan be used to carry or store desired program code means in the form ofinstructions or data structures and that can be accessed by ageneral-purpose or special-purpose computer, or a general-purpose orspecial-purpose processor. Also, any connection is properly termed acomputer-readable medium. For example, if the software is transmittedfrom a website, server, or other remote source using a coaxial cable,fiber optic cable, twisted pair, digital subscriber line (DSL), orwireless technologies such as infrared, radio, and microwave, then thecoaxial cable, fiber optic cable, twisted pair, DSL, or wirelesstechnologies such as infrared, radio, and microwave are included in thedefinition of medium. Disk and disc, as used herein, include CD, laserdisc, optical disc, digital versatile disc (DVD), floppy disk andBlu-ray disc where disks usually reproduce data magnetically, whilediscs reproduce data optically with lasers. Combinations of the aboveare also included within the scope of computer-readable media.

As used herein, including in the claims, “or” as used in a list of items(e.g., a list of items prefaced by a phrase such as “at least one of” or“one or more of”) indicates an inclusive list such that, for example, alist of at least one of A, B, or C means A or B or C or AB or AC or BCor ABC (i.e., A and B and C). Also, as used herein, the phrase “basedon” shall not be construed as a reference to a closed set of conditions.For example, an exemplary step that is described as “based on conditionA” may be based on both a condition A and a condition B withoutdeparting from the scope of the present disclosure. In other words, asused herein, the phrase “based on” shall be construed in the same manneras the phrase “based at least in part on.”

In the appended figures, similar components or features may have thesame reference label. Further, various components of the same type maybe distinguished by following the reference label by a dash and a secondlabel that distinguishes among the similar components. If just the firstreference label is used in the specification, the description isapplicable to any one of the similar components having the same firstreference label irrespective of the second reference label, or othersubsequent reference label.

The description set forth herein, in connection with the appendeddrawings, describes example configurations and does not represent allthe examples that may be implemented or that are within the scope of theclaims. The term “exemplary” used herein means “serving as an example,instance, or illustration,” and not “preferred” or “advantageous overother examples.” The detailed description includes specific details forthe purpose of providing an understanding of the described techniques.These techniques, however, may be practiced without these specificdetails. In some instances, well-known structures and devices are shownin block diagram form in order to avoid obscuring the concepts of thedescribed examples.

The description herein is provided to enable a person skilled in the artto make or use the disclosure. Various modifications to the disclosurewill be readily apparent to those skilled in the art, and the genericprinciples defined herein may be applied to other variations withoutdeparting from the scope of the disclosure. Thus, the disclosure is notlimited to the examples and designs described herein, but is to beaccorded the broadest scope consistent with the principles and novelfeatures disclosed herein.

What is claimed is:
 1. A method for wireless communications, at a userequipment (UE), comprising: transmitting a request message to a networkdevice while operating in a power conserving mode; monitoring a physicaldownlink control channel for a response message to the request message,the response message comprising a random access preamble indexassociated with the request message; and receiving the response messageon the physical downlink control channel.
 2. The method of claim 1,further comprising: determining a radio network temporary identifier(RNTI) based at least in part on the random access preamble index; andunscrambling a cyclic redundancy check (CRC) of the response messagewith the RNTI.
 3. The method of claim 1, further comprising: identifyinga bit field pattern indicating a radio network temporary identifier(RNTI) for the response message is calculated based at least in part onthe random access preamble index.
 4. The method of claim 1, furthercomprising: identifying a first subset of bits of the random accesspreamble index in a radio network temporary identifier (RNTI); andidentifying a second subset of bits of the random access preamble indexin a payload of the response message.
 5. The method of claim 1, furthercomprising: identifying the random access preamble index in a payload ofthe response message.
 6. The method of claim 1, further comprising:identifying a payload of the response message based at least in part ona value of a frequency assignment bit field of the response message. 7.The method of claim 6, wherein the payload is further identified basedat least in part on one or more reserved bits of the response message.8. The method of claim 1, wherein the response message is anacknowledgment of the request message.
 9. The method of claim 1, whereinthe response message comprises information in response to the requestmessage.
 10. The method of claim 9, wherein the request message is asystem information request and the information in response to therequest message comprises timing or frequency information related towhen a requested system information will be transmitted.
 11. The methodof claim 9, wherein the request message is a positioning referencesignal (PRS) request, and the information in response to the requestmessage comprises a configuration for a PRS to be transmitted inresponse to the PRS request.
 12. The method of claim 1, wherein theresponse message comprises a single random access response.
 13. Themethod of claim 1, wherein a type of the response message is indicatedby a type-identifying field in a radio network temporary identifier(RNTI).
 14. A method, at a network device, for wireless communications,comprising: receiving a request message from a user equipment (UE)operating in a power conserving mode; generating, in response to therequest message, a response message comprising a random access preambleindex corresponding to the request message; and transmitting thegenerated response message on a physical downlink control channel. 15.The method of claim 14, further comprising: determining a radio networktemporary identifier (RNTI) based at least in part on the random accesspreamble index; and scrambling a cyclic redundancy check (CRC) of thegenerated response message with the determined RNTI.
 16. The method ofclaim 14, further comprising: setting a bit field pattern of thegenerated response message indicating a radio network temporaryidentifier (RNTI) is calculated based at least in part on the randomaccess preamble index.
 17. The method of claim 14, further comprising:including a first subset of bits of the random access preamble index ina radio network temporary identifier (RNTI); and including a secondsubset of bits of the random access preamble index in a payload of thegenerated response message.
 18. The method of claim 14, furthercomprising: determining a payload for the generated response messagecomprising the random access preamble index.
 19. The method of claim 14,further comprising: indicating a payload for the generated responsemessage comprises the random access preamble index based at least inpart on a value of a frequency assignment bit field.
 20. The method ofclaim 19, wherein: indicating the payload comprises the random accesspreamble index is further based at least in part on one or more reservedbits of the generated response message.
 21. The method of claim 14,wherein the generated response message is an acknowledgment of therequest message.
 22. The method of claim 14, wherein the generatedresponse message includes information in response to the requestmessage.
 23. The method of claim 22, wherein the request message is asystem information request and the information in response to therequest message comprises timing or frequency information related towhen a requested system information will be transmitted.
 24. The methodof claim 22, wherein the request message is a positioning referencesignal (PRS) request, and the information in response to the requestmessage comprises a configuration for a PRS to be transmitted inresponse to the PRS request.
 25. The method of claim 14, furthercomprising: identifying a single random access response for thegenerated response message, wherein the generated response message istransmitted on the physical downlink control channel based at least inpart on the identifying.
 26. The method of claim 14, wherein a type ofthe generated response message is indicated by a type-identifying fieldin a radio network temporary identifier (RNTI).
 27. A user equipment(UE) for wireless communications, comprising: a processor, memory inelectronic communication with the processor; and instructions stored inthe memory and executable by the processor to cause the UE to: transmita request message to a network device while operating in a powerconserving mode; monitor a physical downlink control channel for aresponse message to the request message, the response message comprisinga random access preamble index associated with the request message; andreceive the response message on the physical downlink control channel.28. The UE of claim 27, wherein the instructions are further executableby the processor to cause the UE to: determine a radio network temporaryidentifier (RNTI) based at least in part on the random access preambleindex; and unscramble a cyclic redundancy check (CRC) of the responsemessage with the RNTI.
 29. A network device for wireless communications,comprising: a processor, memory in electronic communication with theprocessor; and instructions stored in the memory and executable by theprocessor to cause the network device to: receive a request message froma user equipment (UE) operating in a power conserving mode; generate, inresponse to the request message, a response message comprising a randomaccess preamble index corresponding to the request message; and transmitthe generated response message on a physical downlink control channel.30. The network device of claim 29, wherein the instructions are furtherexecutable by the processor to cause the network device to: determine aradio network temporary identifier (RNTI) based at least in part on therandom access preamble index; and scramble a cyclic redundancy check(CRC) of the generated response message with the determined RNTI.